1. Field of the Invention
This invention relates to an ink jet printer and an ink tank for supplying ink to a recording head in the printer and in particular to a printer with an ink tank that can be detached by the user for replacement.
2. Description of the Related Art
Hitherto, an ink jet cartridge made up of a head cartridge having an ink jet recording head and a tank holder and an ink tank that can be attached to or detached from the tank holder has been known as an ink jet cartridge used with an ink jet recorder. With such an ink jet cartridge, when ink is consumed, only the ink tank may be replaced; the ink jet cartridge is advantageous to reduction in costs as compared with an ink jet cartridge with a head cartridge and an ink tank molded in one piece.
However, in an ink jet printer using such an ink tank, when the ink tank is attached at the ink tank replacement time, ink leaks from an ink supply hole made in the bottom of the ink tank and is deposited on the inside of the ink jet recorder or makes user's hand dirt, etc. Further, when the ink tank is replaced, bubbles are drawn into an ink flow passage, thereby causing an ink jet failure to occur, lowering image quality.
As one of solutions to this problem, a structure is effective wherein a joint part is provided with an ink reservoir without supplying ink directly from an ink-impregnated member being disposed in an ink tank for holding ink. However, in this structure, an ink leakage in the joint part introduces another problem.
To prevent ink from leaking in the joint part, a structure wherein an ink outlet of an ink tank is made of a rubber stopper and an ink supply metal needle is made to pierce the rubber stopper for direct liquid connection to an ink flow passage to a recording head is known, for example, as disclosed in Japanese Patent Laid-Open No. Hei 3-92356. The ink supply needle in the structure uses a pipe having corrosion resistance to ink and the pipe has a tip made extremely sharp so as to be able to pierce the rubber stopper and is formed on a side face with an ink supply hole about 1 mm in diameter. Such an ink supply needle enables liquid connection and the ink supply port of the ink tank is closed by the elastic force of the rubber stopper, preventing ink from leaking. However, if the user handles the ink supply needles carelessly, he or she may touch the sharp pipe tip and be hurt. Further, since the ink supply needle itself has a small inner diameter, a broken piece of the pierced rubber stopper is mixed into the ink supply needle and interferes with an ink supply.
As another solution, a structure wherein an ink outlet is made up of two rings and a supply port seal is available, for example, as disclosed in Japanese Patent Laid-Open No. Hei 7-125238. In this structure, an ink supply metal needle is not made to pierce a rubber stopper, thus the risk of a broken piece of the rubber stopper mixed into the ink supply needle is reduced, but a sharp pipe must be still used, introducing the problem that the user may touch the sharp pipe tip and be hurt.
As another solution, a structure wherein the ink supply hole tip is provided with a packing member having a through hole and the through hole is sealed by a seal member, then an ink supply tube having a comparatively dull tip is made to pierce the seal member is available, for example, as described in Japanese Patent Laid-Open No. Sho 50-74341. However, the art involves a problem of leakage of a minute amount of ink from space between the ink supply tube piercing the seal member and the seal member.
Hitherto, the following art described in Japanese Patent Laid-Open Nos. Hei 6-312515 and Hei 6-320749 has been known as a method for solving the problem:
In the art described here, a cylindrical ink supply tube projecting outward is disposed on the ink jet recording head side and is formed at the tip with a plurality of projections. On the other hand, a breakable heat-seal film made of an ink non-permeability material is put on an ink supply hole made in the bottom of an ink tank. When the ink tank is attached, the heat-seal film is broken by the projections of the ink supply tube tip and the ink supply tube is connected to the ink supply hole.
However, in the structure, a broken piece of the heat-seal film broken by the projections of the ink supply tube tip may block the ink supply tube partially, making it impossible to supply ink stably.
The following art shown in FIGS. 28A and 28B are possible as a method for solving the problem with the above art:
FIGS. 28A and 28B are schematic illustrations of an ink tank T and a recording head section H designed for solving the problem with the above art; FIG. 28A is an overall illustration and 28B is an enlarged view of the main part of the ink tank T. A ring-like abutment part 102 projecting like a ring so as to make an ink supply hole 101 inside the abutment part 102 is disposed at the bottom of the ink tank T. An ink inflow hole 103 into which ink supplied from the ink supply hole 101 flows is made in the ink jet recording head H. An abutment member 103a abutting the ring-like abutment part 102 when the ink tank T is attached is disposed in the ink inflow hole 103.
In the structure, when the ink tank T is not used, a soft seal material 104 is put on the tip of the ring-like abutment part 102 of the ink tank T with an adhesive or by heat sealing, etc., for sealing the ink supply hole 101. When the ink tank T is used, the worker peels off the seal material 104, attaches the ink tank T to the ink jet recording head H, and abuts the ring-like abutment part 102 against the abutment member 103a.
In the art structure, the seal material 104 is put on the tip of the ring-like abutment part 102 by bonding or heat sealing, but the area of the bonding or heat sealing portion is small, thus the seal material 104 easily peels off. Therefore, when the ink tank T is not used and is stored, it is feared that the seal material 104 will peel off, allowing ink to leak.
In heat sealing, when the seal material 104 is heat-sealed in the contact portion with the tip of the ring-like abutment part 102, not only the seal material 104, but also the sharp-pointed tip of the ring-like abutment part 102 melts. If the sharp-pointed tip of the ring-like abutment part 102 melts, when the ink tank T is attached to the recording head H, the tip of the ring-like abutment part 102 is not engaged in the abutment member 103a and ink leakage easily occurs.
In bonding, when the seal material 104 put on the tip of the ring-like abutment part 102 is peeled off at the time of attaching the ink tank T, the adhesive can be left on the tip of the ring-like abutment part 102. If the adhesive is left on the tip of the ring-like abutment part 102, when ink is supplied after the ink tank T is attached, it is feared that the adhesive will dissolve in the ink, deteriorating the ink.